Analysis of phase-matching conditions in flexural-wave modulated fiber Bragg grating

• Published in: Journal of lightwave technology Vol. 20; no. 2; pp. 311 - 315
• Main Authors: SUN, Nai-Hsiang, CHOU, Chih-Cheng, CHANG, Ming-Jen, LIN, Chih-Nan, YANG, Chih-Chung, KIANG, Yean-Woei, LIU, Wen-Fung
• Format: Journal Article
• Language: English
• Published: New York, NY IEEE 01.02.2002; Institute of Electrical and Electronics Engineers; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Acoustic diffraction; Acoustic reflection; Applied sciences; Bragg gratings; Circuit properties; Cladding; Communication switching; Diffraction gratings; Electric, optical and optoelectronic circuits; Electronics; Exact sciences and technology; Fiber gratings; Fibers; Frequency conversion; Integrated optics. Optical fibers and wave guides; Joining; Microorganisms; Network switching; Optical and optoelectronic circuits; Phase modulation; Reflection; Refractive index; Wavelength division multiplexing; Wavelengths; Operation study; Mode coupling; Single mode fiber; Optical telecommunication; Step index; Refraction index; Bragg grating; Wavelength division multiplexing; Optical fiber communication
• ISSN: 0733-8724; 1558-2213
• DOI: 10.1109/50.983246

Effective refractive indexes of the core mode and various cladding modes of a tapered single-mode step-index fiber were calculated for identifying the cladding modes of phase matching for coupling with the core mode, caused by a prewritten Bragg grating together with an applied flexural wave (microbending) in the tapered region. With these coupling mechanisms, the previously reported reflection wavelength switching could be well interpreted. Between the core mode and a cladding mode, the Bragg grating caused contradirectional coupling and the flexural wave resulted in codirectional coupling of either first- or second-order diffraction. Meanwhile, the period of the acoustic-induced flexural wave was calibrated to be a few hundreds of micrometers. Based on the phase-matching calculations, the relationship between cladding radius and flexural wave period with a chosen wavelength for reflection switching was provided. Such design considerations should be helpful in implementing wavelength switches, based on flexural wave modulation of fiber Bragg grating (FBG), for the applications of wavelength division multiplexing (WDM) fiber communications.